Really weird earth loop with T112

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This topic contains 3 replies, has 3 voices, and was last updated by Profile photo of Mr-B Mr-B 15 years, 1 month ago.

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  • #22056
    Profile photo of

    Hi all,
    Just had a bit of a weird one on my shiny new toy….

    Ok, so I have a bog standard domestic cd player at FOH for incidental music, it is a class II (double insulated) device and as such should be pretty much immune to earth loop sillyness.

    I connect it via a pair of 1M unbalanced phono leads to the pair of phonos provided for (presumably) this sort of use on the back of the surface.

    It Buzzes! Confused, I try adding a short case to case bond, the buzz stops, but now there is a low level hum! I slap a gate on it and get on with the gig.

    PAT testing the CD player reveals that there is NO measurable leakage, so it is not a problem there.

    The CD player is plugged into the same power as the surface (Not that that should matter given it is class II).

    Even more weirdly, it appears that without the additional earth bond, I get pure difference (L-R) riding on the buzz, almost like the phono sockets do not have their shell connected to the reference ground at all (Sort of a failed attempt to apply AES 48 to unbalanced inputs or something)…..

    I am beginning to suspect that there is something very funky with those unbalanced inputs?

    Has anyone else seen this sort of behaviour?

    Regards, Dan.

    Profile photo of millst

    Have you tried plugging another device into the inputs?
    You need to isolate the problem by replacing everything else and trying it.

    Try it with a different cable (different brand)
    Then try a different CD player.

    If you get the same thing with both of these then the problem is the i-Live.

    Profile photo of

    Yea, I have tried all the obvious fixes.

    (Different player, different cables), it still only shows difference signal unless you add a parallel earth path.

    Time to call the dealer and get the thing picked up I guess.

    Regards, Dan.

    Profile photo of Mr-B

    Is it me or does this sound like a ground is missing on the Phono inputs? Now I know why I like those XLR connectors, or even the digital inputs.

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